It has long been known that peroxygen bleaches are effective for stain and/or soil removal from fabrics, but that such bleaches are temperature dependent. At a laundry liquor temperature of 60.degree. C., peroxygen bleaches are only partially effective. As the laundry liquor temperature is lowered below 60.degree. C., peroxygen bleaches become relatively ineffective. As a consequence, there has been a substantial amount of industrial research to develop bleaching systems which contain an activator that renders peroxygen bleaches effective at laundry liquor temperatures below 60.degree. C.
Numerous substances have been disclosed in the art as effective bleach activators. One widely-used bleach activator is tetraacetyl ethylene diamine (TAED). TAED provides effective hydrophilic cleaning especially on beverage stains, but has limited performance on dingy stains and body soils. Another type of activator, such as nonanoyloxy-benzenesulfonate (NOBS) and other activators which generally comprise long chain alkyl moieties, is hydrophobic in nature and provides excellent performance on dingy stains.
It would seem that a combination of bleach activators, such as TAED and NOBS, would provide an effective detergent composition which would perform well on both hydrophilic and hydrophobic soils and stains. However, many of the hydrophilic activators developed thus far, including TAED, have been found to have limited efficacy, especially at laundry liquor temperatures below 60.degree. C. Another consideration in the development of consumer products effective on both types of soils is the additional costs associated with the inclusion of two or more bleach activators. Accordingly, it is of substantial interest to the manufacturers of bleaching systems to find a less expensive type of hydrophilic bleaching activator.
By the present invention, it has now been discovered that the class of bleach activators derived from hydrophilic N-acyl caprolactams performs very well when combined with the cleaning performance of hydrophobic alkanoyloxybenzenesulfonate and has the added benefit of being relatively inexpensive to manufacture. Accordingly, the present invention solves the long-standing need for an inexpensive bleaching system which performs efficiently and effectively at low temperatures and under mixed soil load conditions, especially mixtures of hydrophobic and hydrophilic soils.